The overall objective of the proposed research is to contribute to an improved understanding of the etiology of periodontal disease by continuing studies of dental plaque antigens and antibodies to them in gingiva affected by periodontitis. Based on previous findings of antigen in the gingiva, the project will attempt: (1) to determine if the antigens exist in immune complexes, using double-label immunofluorescence; (2) to more precisely describe the location of the antigens by immunohistochemistry for electron microscopy; and (3) to begin fractionation of the mixture of plaque antigens previously used, so that individual components may be tested. Additionally, antibody to extracts of pure cultures of oral bacterial will be searched for in gingiva, using immunofluorescent techniques.